Lianas are woody vines that grow in tropical forests. Researchers measured liana abundance (stems/ha) in several plots in the central Amazon region of Brazil. The plots were classified into two types: plots that were near the edge of the forest (less than 100 meters from the edge) or plots far from the edge of the forest.The raw data are given and are summarized in the table.
|
|
|
n MEAN
|
SD
|
|
|
Near Far
|
34 438
34 368
|
125
114
|
|
|
|
|
|
|
NEAR
|
|
|
FAR
|
|
|
639
|
601
|
600
|
470
|
339
|
384
|
|
605
|
581
|
555
|
309
|
395
|
393
|
|
535
|
531
|
466
|
236
|
252
|
407
|
|
437
|
423
|
380
|
241
|
215
|
427
|
|
376
|
362
|
350
|
320
|
228
|
445
|
|
349
|
346
|
337
|
325
|
267
|
451
|
|
320
|
317
|
310
|
352
|
294
|
493
|
|
285
|
271
|
265
|
275
|
356
|
502
|
|
250
|
450
|
441
|
181
|
418
|
540
|
|
436
|
432
|
420
|
250
|
425
|
590
|
|
419
|
407
|
|
266
|
495
|
|
|
702
|
676
|
|
338
|
648
|
|
(a) Make normal probability plots of the data to confirm that the distributions are mildly skewed.
(b) Conduct a test to compare the two types of plots at α = 0.05. Use a nondirectional alternative.
(c) Apply a logarithm transformation to the data and repeat parts (a) and (b).
(d) Compare the tests from parts (b) and (c).What do these results indicate about the effect on a test of mild skewness when the sample sizes are fairly large?